A Wellington father says he would happily vaccinate against tetanus, but bureaucrats have undermined a parent's choice by combining the shot with the diphtheria vaccine.

Ian Williams spoke last week of his heartbreak watching son Alijah, 7, battle tetanus because he wasn't immunised. Williams is now calling on other parents to believe the science rather than act like a "hippy" when making the decision about vaccination.

Tom White of Wellington told the Sunday Star-Times that like any parent, he found the story about Alijah gut-wrenching but he felt parents were not actually given a choice when it came to vaccinations because you cannot "obtain a tetanus shot without also having a diphtheria vaccination imposed", he said.

"For whose benefit and with whose blessing was this unilateral change made?" he asked. "Likely it was a bureaucratic or business decision made by or with the pharmaceutical industry. [It] undermines any pretence at informed consent."

He said he was not an active resister but a selective participant in the vaccination programme.

"Before even starting to address the active resisters, health authorities could hone their approach towards parents like me who insist on being active participants rather than passive submitters.

"Please make available a tetanus-only vaccination and I'll happily pay for it, if need be."

The Ministry of Health confirmed a single tetanus vaccine is not available in New Zealand. Tetanus has been offered as a combination vaccine since 1960 and a tetanus-only shot is no longer manufactured by the major international drug companies.

Due Dashfield, the Community Health Service improvement manager, said combining vaccines means more diseases can be immunised against with a single vaccination.

"The content of the vaccines given today is so well refined that children actually receive fewer antigen components than their parents would have, despite the combining of immunisations."

Diphtheria is a rare but contagious bacterial infection that causes severe throat and breathing difficulties. One in 15 people who catch diphtheria die. About 10 per cent of people vaccinated against the disease will experience inflammation or a fever. Serious adverse reactions are rare. The latest figures show 93 per cent of 2-year-olds are now fully immunised, up from 73 per cent in 2008.